word-extractor/lib/ole-allocation-table.js

Node.js package to read Word .doc files

const ALLOCATION_TABLE_SEC_ID_FREE               = -1;
const ALLOCATION_TABLE_SEC_ID_END_OF_CHAIN       = -2;   // eslint-disable-line no-unused-vars
const ALLOCATION_TABLE_SEC_ID_SAT                = -3;   // eslint-disable-line no-unused-vars
const ALLOCATION_TABLE_SEC_ID_MSAT               = -4;   // eslint-disable-line no-unused-vars

class AllocationTable {

  constructor(doc) {
    this._doc = doc;
  }

  load(secIds) {
    const doc = this._doc;
    const header = doc._header;
    this._table = new Array(secIds.length * (header.secSize / 4));
    return doc._readSectors(secIds)
      .then((buffer) => {
        for (let i = 0; i < buffer.length / 4; i++) {
          this._table[i] = buffer.readInt32LE(i * 4);
        }
      });
  }
  
  getSecIdChain(startSecId) {
    let secId = startSecId;
    const secIds = [];
    while (secId > ALLOCATION_TABLE_SEC_ID_FREE) {
      secIds.push(secId);
      const secIdPrior = secId;
      secId = this._table[secId];
      if (secId === secIdPrior) { // this will cause a deadlock and a out of memory error
        break;
      }
    }
  
    return secIds;
  }
  
}

module.exports = AllocationTable;